Approach to the Blues: A Highly Flexible Route to the Azulenes


  • We thank Prof. P. Dumy for his interest in our research, the Research Ministry for fellowship awards to S.C. and Y.C., and the Université Joseph Fourier and the CNRS (UMR 5616, FR 2607) for financial support.


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A palette of blues: Chlorobicyclo[5.3.0]decatrienones are readily prepared from cycloheptatrienes by cycloaddition of dichloroketene, ring expansion with a diazoalkane, and dehydrochlorination in dimethylformamide. These compounds are used as intermediates in the regiocontrolled synthesis of a wide variety of natural and nonnatural azulenes (see scheme).